Treadle-actuated closures

ABSTRACT

A closure structure (e.g., curtains, doors, blinds, etc.) is actuated between &#39;&#39;&#39;&#39;open&#39;&#39;&#39;&#39; and &#39;&#39;&#39;&#39;closed&#39;&#39;&#39;&#39; positions by a footoperated treadle assembly operatively connected to one or more pivotally mounted actuating arms which engage the closure elements. The treadle assembly includes a toggle latch mechanism which controls its operation e.g. to permit the closure elements to open and then close upon a single actuation and release of the treadle, or to permit the closure elements to open and then close, or vice versa, in response to successive actuations of the treadle respectively, and/or to adjust the quiescent position of the closure structure in its open or semi-open position. The overall system may comprise a support bar having drapes depending therefrom, adapted to be mounted adjacent the top of a door frame, cooperating with a treadle and associated toggle latch mechanism positioned at floor level in or adjacent said door frame and coupled to the actuating arm or arms mounted on the support bar by simple cord or cable linkages.

United States Patent [191 Kober et al.

[ June 11, 1974 I [22 Filed:

[ TREADLE-ACTUATED CLOSURES [75] Inventors: Leslie Z. Kober, Springfield;

Maurice C. Bailey, Fairfax, both of Va.

[73] Assignee: Log Etronics lnc., Springfield, Va.

Sept. 13, 1972 [2]] Appl. No.: 288,833

[52] US. Cl 160/123, 160/330, 160/349 [51] Int. Cl A47h l/00 [58] Field of Search 160/123-l26, 160/330, 340, 349, 349 D; 49/132-134, 263-274, 379

[56] References Cited I UNITED STATES PATENTS 268,282 11/1882 Reeves 49/263 1,463,079 7/l923 Givens... 49/267 l.746,l43 2/l930 Callahan [60/340 2204, 177 6/1940 Ebaugh 49/132 Primary E.\'aminerPeter M. Caun Attorney, Agent, or FirmElli0tt I. Pollock [5 7] ABSTRACT A closure structure (e.g., curtains, doors, blinds, etc.) is actuated between open and closed positions by a foot-operated treadle assembly operatively connected to one or more pivotally mounted actuating arms which engage the closure elements. The treadle assembly includes a toggle latch mechanism which controls its operation e.g. to permit the closure elements to open and then close upon a single actuation and release of the treadle, or to permit the closure elements to open and then close, or vice versa, in response to successive actuations of the treadle respectively, and/or to adjust the quiescent position of the closure structure in its open or semi-open position. The-overall system may comprise a support bar having drapes depending therefrom, adapted to be mounted adjacent the top of a door frame, cooperating with a treadle and associated toggle latch mechanism positioned at floor level in or adjacent said door frame and coupled to the-actuating arm or arms mounted on the support bar by simple cord or cable linkages.

8 Claims, 13 Drawing Figures PATENTEBJUH 1 1 M 3,8 1 S .656

SHEET 1 or 4 TREADLE-ACTUATED CLOSURES BACKGROUND OF THE INVENTION Various forms of treadle-actuated closure structures have been suggested over the years. Such structures have been used, for example, inv conjunction with garage doors to cause the doors to be automatically opened in response to the weight of a vehicle approaching the door, with thedoors closing automatically after the vehicle has passed into a garage. Related structures have been employed in other applications, e.g., to open furnace doors, to open and close animal pasture areas, to open and close gates extending across a roadway, etc.

For the most part, the structures which have been suggested in the past have comprised complicated linkages and gear trains. Even in those cases where the linkages have included cables or cords as part of the operating mechanism, additional mechanisms have been considered necessary to effect appropriate transfer of forces from an actuating mechanism to the closure elements operated thereby.As a result, treadle operated closures which have been suggested heretofore have been large and unwieldy, and expensive to construct and maintain. These disadvantages have been accompanied by the further disadvantage that the treadle operated systems suggested heretofore normally exhibit a single mode of operation, e.g., application of force to the treadle mechanism opens the closure structure, with subsequent removal of said treadle-applied force producing an automatic reclosing of the structure; and no means have been provided for varying the operating mode in circumstances where a variation might be desirable.

The present invention, recognizing the disadvantages of the prior art, is concerned with an improved treadleactuated closure structure characterized by a structural configuration which is far simpler than anything suggested heretofore, lending itself to ready portability for installation in preexisting building structures such as a door frame or. adjacent a window frame, and further characterized by a novel treadle assembly havinga toggle latch mechanism which achieves closure actuation operating characteristics different from those of the prior art, and which permits ready variation in those operating characteristics as may be desirable under different conditions of usage of the closure structure.

The assembly of the present invention lends itself to I use in conjunction with a variety of different closure structures, the term being employed generically hereinafter and in the appended claims to designate various structures such as drapes, curtains, single and double hinged doors, single and double folding doors, roller blinds, and Venetian blinds, usable in a variety of different environments such as photographic darkrooms, clothing changing rooms, tents, home doors and/or windows; etc.

SUMMARY OF THE INVENTION In accordance with the preferred embodiments of the present invention, the treadle-actuated closure structure constitutes two main parts, i.e., a support member adapted to carry a movable closure structure thereon, and a treadle actuating mechanism of novel design adapted to be mounted at floor level for operating the closure structure between fully or partially open and closed positions.

In the preferred embodiment of the invention, to be described hereinafter, the support member comprises a support bar which may be retained in place by an appropriate mounting hanger or bracket, or which may take the form of a telescopic bar adjustable in length, which has a pair of drapes depending therefrom adapted to be opened away from one another from a central position. The support bar further includes an operating mechanism for manipulating the closure structure. In the preferred embodiment of the invention, the operating mechanism constitutes a pair of elongated operating arms mounted concentrically to rotate about a common support spindle disposed adjacent the center of the support bar; and the support bar further carries a pair of pulleys adapted to guide cords or cables extending from the floor mounted treadle assembly to said operating arms.

The treadle assembly comprises a pair of aligned treadle plates which may be mounted to bridge the door frame in which the support bar is located, or the plates may both be located to one side or the other of said door frame. The innermost ends of the treadle plates are mounted for rotation on a pair of bars extending between a pair of rocker plates each of which includes 'a pair of outstanding pins adapted to slide within portions of a dual-slot detent plate disposed adjacent said rocker plate. Each detent plate includes at least two slots of different height; and as weight is applied to the treadle plates, the rocker plates and pins outstanding therefrom are caused to move in vertical and angular directions between said slots to cause a selective treadle latching operation. The operation can be'such that, as a person steps along the two treadle plates in sequence for the first time, a normally closedclosure structure opens and remains fully or partially open until the person again steps upon the two treadle plates in the opposite sequence, e.g., while passing in the opposite direction through the opening defined by the closure structure. Alternatively, the closure structuremay be normally open, may be caused to close bethe opposite direction. The detent plates can be so constructed that either mode of operation is facilitated by a simple adjustment in the plates. The detent plates can also be made adjustable to permit control of the extent to which theclosure structure remains open when it has been opened, and also to eliminate the latching operation entirely so that the closure structure automatically opens and closes in response to the application of weight to and removal of weight from the treadle mechanism.

Spring mechanisms are coupled between the rocker plates and a fixed structure, e.g., the sides of the door frame, to urge the innermost ends of the treadle plates toward their uppermost positions when no weight is applied thereto, thereby to achieve the desired latching operation. The degree of force applied by the springs may, if desired, be adjustable, to achieve a weight discrimination, e.g., to permit the treadle actuated closure structure to be operated by an adult but not by a child or a small animal.

BRIEF DESCRIPTION OF THE DRAWINGS The foregoing construction, operation, and advantages of the present invention will become more readily appreciated from the following description and accompanying drawings in which:

FIGS. 1A and 1B are diagrammatic representations of an improved treadle-actuated closure structure, employing drapes, in closed and open positions respectively;

FIG. 2 is a detail view of a portion of the treadle assembly illustrating the rocker plate employed in the toggle latch mechanism;

FIG. 3 is an exploded detail view of the toggle latch mechanism employed in the treadle assembly;

FIG. 3A illustrates a modified form of detent plate which may be employed;

FIGS. 4A through 4F inclusive diagrammatically illustrate, in sequence, the operation of the toggle latch mechanism;

FIG. 5 illustrates a further type of detent plate which maybe employed; and

. FIG. 6 diagrammatically illustrates an alternative positioning of the treadle assembly relative to the closure structure.

, "DESCRIPTION oF'TaE PREFERRED EMBODIMENTS As described previously, the closure structure of the present invention may take a variety of forms and may be utilized in a variety of applications. The nature of the'closure structureemployed, and the mode of operation selected forthat closure structure,.will accordingly depend upon the particular application involved. By way of example, when the closure structure is employed at the entry of a photographic darkroom, the closure structure should be opaque and the treadle assembly associated therewith may be adjusted to exhibit a mode of operation wherein the closure structure is normally open but is caused to automatically close as a person enters the darkroom, and vice versa. When the closure structure is employed atthe entry of a storage area, the mode of operation can be such that, as a person enters the area, e.g., with his arms full of material to be stored therein, the closure structure automatically opensgand, thereafter, automatically closes when the person leaves the storage area. When the closure structure is intended to be decorative, e.g., curtains covering a window, the closure structure can be translucent to light. r

The embodiment of the invention shown in FIGS. 1A and 1B is of the drape" or curtain type adapted to be employed in any of the various different environments discussed above. It constitutes a support bar 10 pro vided with a pair of hangers 11 for suspending the support bar 10 at a position adjacent the upper portion'of a door frame or other fixed structure, diagrammatically depicted at 12. Instead of using hangers 11, the support bar 10 can be a tension-pole type of structure, e.g., of

telescopic configuration. Other variations will be ap parent. p

v A, pair ofdrapes or curtains 13a and 13b are suspended from supportbar 10. When the present invention is to be employed in a darkroom, the curtains 13a and l3b can be of opaque plastic-coated clothconstruction and should be of sufficient length to completely cover the darkroom entry when in closed position, e.g., the lowermost edges of the curtains can drape over the floor. In addition, auxiliary elements, not shown, can be used to assist in making the closure completely light-tight, e.g., permanent magnets can be mounted on portions of the curtains and at portions of the adjacent floor structure to augment the lightsealing function.

The curtains 13a and 13b are manipulated between their open and closed positions by an actuating assembly carried by support bar 10 which is, in turn, operated by a treadle assembly mounted at floor level. These two portions of the structure can be separate from one another to render the overall system highly portable; and once the support bar assembly and associated actuating structure is mounted adjacent the top of a door frame, and the treadle assembly is mounted adjacent the bottom of said door frame, an operative interconnection is achieved therebetween by a simple cord or cable configuration.

The actuating portions of the system, associated with support bar 10, may comprise a pair of elongated actuating arms 14 and 15, disposed ingenerally vertical orientation when the closure structure is in its closed position (see FIG. 1A) and mounted for pivotal or rotational movement relative to opposing sides of support bar 10 upon a common pivot 16 disposed adjacent the center of bar l0,'i.e., at a location adjacent the parting line between curtains 13a and 13b. The support bar assembly may further include a pulley l7 mounted at one end thereof on the forward side of said support bar 10, corresponding to the positional mounting of actuating arm 14, and a further pulley mounted at the other end of support bar 10, on the opposite side thereof corresponding to the positional mounting of actuating arm The treadle assembly comprises a pair of treadle plates 19 and 20 which are aligned with one another and bridge the opening associated with the-closure structure. The outermost ends of the treadle plates 19 and 20 are positioned at floor level, and each of said plates is inclined upwardly toward its innermost end to permit the plates to be depressed, for actuation purposes, by a person stepping along the plates from one to the next. The two plates 19 and 20 are'associated, in common, with a toggle latch mechanism generally designated 21 (to be described in further detail hereinafter inv reference to FIGS. 2 et seq). A pair of cords, cables, rods, or the like, 22a and 22b extend upwardly from the treadle assembly over pulleys 17 and 18 respectively to attachment points located respectively on each of the actuating arms 14 and 1-5, at positions above pivot 16.

The two actuating arms 14 and 15 are connected, below pivot 16, to the curtains 13a and 1311 respectively. Application of forces to the treadle plates 19 and 20 depresses said treadle plates and, by pulling downwardly on the cords 22a and 22b, causes the actuating arms 14 and 15 to rotate about their commonpivotv 16 to open curtains 13a and 13b away from one another, as illustrated in FIG. 1B. In practice, a depression of substantially one-half inch at the innermost ends of the treadle plates 19 and 20 moves the inner edge of each of curtains 13a and 13b approximately l5inches, to produce an opening of substantially 30 inches therebetween. v

When forces are removed from the treadle plates 19 and 20 (disregarding for the moment the operation of the toggle latch mechanism 21) the weight of actuating arms 14 and 15 and their attached curtains causes the structure to close to the position shown in FIG. 1A, under the force of gravity. This closure action may be augmented, if desired, by a pair of springs 24 (only one of which is shown) extending between the inner edges of the treadle plate 19, and a fixed structure such as structure 12. Springs 24 urge the innermost ends of the treadle plates in an upward direction. A similar operation may be achieved by other types of resilient structure, e.g., a sponge-like pad may be disposed beneath the treadle plates to urge them upwardly.

In the operation of the system shown in FIGS. 1A and 18, as thus far described, the application of an actuating-force to one of the treadle plates, e.g., 19, causes the closure structure to open, maintains the closure structure open as the person steps onto the second treadle plate, e.g., 20, whereafter removal of the force from treadle plate 20 then causes the structure to close automatically as the person steps off treadle plate 20. This mode of operation has various practical applications. However, in some cases a different mode of operation is desirable, e.g., it may be desirable to have the curtains 13a and 13b normally closed, with the system operating in a fashion-such that, as a person steps along treadle plate 19, the curtains open in front of him and continue to remain open until the person passes in the reverse direction along the treadle plate 20 to reclose behind him when he steps along and off treadle plate 19. The converse mode of operation may also be desirable, i.e., the curtains may be normally open, may be caused to automatically close behind him as a person steps in sequence from one to the next of the treadle plates, and may then be caused to return to their open position in front of him asa person steps in reverse direction along said treadle plates. It may also be desirable, under some circumstances, to permit a change from one to another of these different modes of operation and, in addition, it may be desirable to permit some adjustment in the extent to which the closure structure remains open'when it is latched into its open position. I These various operating conditions are achieved by the toggle latch mechanism of the present invention.

Referring now to FIGS. 2 and 3, the togglelatch mechanism, referred to above, comprises a pair of rocker plates (only one of which is shown) disposed respectively adjacent opposite side edges of treadle plates 19 and 20, at a location adjacent their innermost edges respectively. The two rocker plates 30 are mounted in fixedly spaced relation to one another by a pair of pivot bars 31 and 32 to which the innermost edges of treadle plates 19 and 20 are affixed. In addition, each rocker plate 30 includes a pair of outstanding pins 33 and 34 disposed in spaced, vertically aligned relation to one another. Lower pin 34 is longer than upper pin 33 for the reasons which will appear is such that the two pins 33 and34 normally extend through longer slot 36 of the detent plate; and the rocker plate is urged to its uppermostposition, with pin 33 seated within the uppermost, semicircular end of longer slot 36, by a spring structure 38. Due to its greater length, pin 34 protrudes beyond the outer face of detent plate 35 by an amount greater than that of pin 33; and the spring structure is attached, as at 39, to the outwardly protruding portion of pin 34 adjacent the exterior of the detent plate 35, at a position where the attachment portion of spring 38 will not interfere with pin 33. Spring 38 extends, via a force adjustment mechanism such as turnbuckle 40, to an attachment point 41 located on a fixed structure such as the side of door frame 12.

The actuating linkages or cables 22a and 22b are connected to the two rocker plates 30. As a result, when forces are applied to the treadle plates 19 and 20, and rocker plates 30 are accordingly moved vertically downward against the force of spring 38, the clords 22a and 22b are also pulled downwardly to effect the closure actuation operations already described in reference to FIG. 1. By using the detent or toggle latch mechanism shown in FIG. 2 and 3, however, the mode of operation differs from that previously described. This will become more readily apparent by reference to FIGS. 4A through 4F inclusive.

Referring initially to FIGS. 3 and 4A, it will be noted that, before actuating force is applied to the treadle plates 19 and 20, rocker plate 30 is held in its uppermost position by spring 38, with pin 33 seated in the upper end of longer slot 36. When a person of suitable weight steps upon treadle plate 19, each rocker plate 30 is forced downwardly against the pull of spring 38', and since both of pins 33 and 34 bear upon the outermost linear side of slot 36 during this phase of the operation, the rocker plate 30 moves vertically downward as depicted by arrow A in FIG. 4B, causing both treadle plates 19 and 20 to move downward by equal amounts. As the person then steps from treadle plate 19 onto treadle plate 20, spring 38 urges pin 34 upwardly; and the continued depression of treadle plate 20 accordingly causes each rocker plate 30 to rotate through an arc, as designated by arrow B in FIG. 4C, until its pin 33' engages the outer side of slot 37. As the person continues his motion, and steps off of treadle plate 20, springs 38 pull each rocker plate 30 upwardly in its tilted position (see arrow C in FIG. 4D) causing pin 33 to now engage, and latch, within the upper semicircular end of shorter slot 37. As a result, the treadle plates are latched into a semi-depressed position. Thus, as forces are applied in sequence from one to the next of plates 19 and 20, the normally closed closure structure is caused to open fully and to remain at least partially open.

A reversal of this operation occurs as a person steps, in the opposite direction, along the treadle plates 20 and 19 in sequence. More particularly, as shown in FIG. 4E, as the person steps onto treadle plate 20 and then onto treadle plate 19, each rocker plate 30 is again depressed (arrow D) and rotated in the opposite direction (arrow E) to cause its pins 33 and 34 to assume the position shown in FIG. 4B (corresponding to the positionv of FIG. 4B). When the person then steps off of treadle plate 19, each rocker plate 30 is pulled upwardly (arrow F) by its associated spring 38 to return the mechanism to a condition corresponding to that of FIG. 4A. As a result, a reverse sequence of applied forces to the two treadle plates and 19 causes the closure structure to be freed from its latched-open condition, and to return to its closed condition.

It will be appreciated that the sequential positions of longer slot 36 and shorter slot 37 in detent plate 35, relative to the direction of travel along the treadle assem bly, determine the'mode of operation, i.e., the shorter of the two slots is disposed, relative to the longer slot, adjacent the downstream one of the two treadle plates to cause the closure structure to be latched into an open condition'after forces are applied sequentially to the upstream treadle plate and then to the downstream treadle plate. If the shorter slot 37 is disposed, relative to the longer slot 36, toward the interior of an enclosure, the closure structure will be latched into an open condition as someone enters the enclosure, and will be returned to its closed condition when the person leaves the enclosure. Conversely, if the shorter slot 37 is disposed, relative to longer slot 36, toward the exterior of the enclosure, the closure structure will be latched into an open condition as a person leaves the enclosure, and will be moved to its closed position when someone enters the enclosure. If it is desired to change from one mode of operation to another, the change could be effected simply by unbolting the two detent plates 35 from. floor plate 36 (see FIG. 3), and then reversing the positions of said two detent plates. To simplify this operation, however, and to permit more ready changes in the mode of operation, the detent plate can take the modified form shown in FIG. 3A.

Referring to FIG. 3A, it will be seen that each detent plate 35a may define a longer slot 36 associated with twoshorter slots 37a and 37b disposed along opposite edges of slot 36. The modified detent plate is associated witha blocking plate 355 which can be removably attached, by screw members, adjacent one or the other edge of longer slot 36, e.g. as shown in broken line in FIG. 3A, to close one or the otherv of the two shorter slots 37a and 37b. The relative positions of the longer and shorter slots in the detent plate can, as a result, be

a point which inhibits rocking motion of rocker plate 30; and it also becomes possible to determine the extent to which the closure structure remains open in its latched condition, by variably increasing the height of slot 37 beyond the height where rocking action can first occur. These further modes of operation are achieved by the modified detent plate structure 50, shown in FIG. 5, which includes a single relatively wide, central slot 51 associated with a blocking plate 52, vertically movable in appropriate guides (not shown), extending horizontally over half of slot 51 and adjustable in vertical directions by means of a screw element 53 passing through a bracket 54 at the top of the detent plate and adapted to be manipulated by a handle 35.

When the movable blocking plate 52 is lowered to r such an extent that rocking action of the rocker plate changed quite readily by simply changing the location 7 of blocking plate 36b. I I

' The amount of actuating force required to achieve the operation described in reference to FIG. 4 depends upon the opposing force which is exerted by springs 38. In some cases, it may be desirable toachieve a weight discrimination to assure that the. closure structure can be properly operated by an adult, but not by a child or v small animal. The turnbuckle 40 illustrated in FIG. 3 permits such weight discrimination to be achieved by permitting variations in the effective force exerted by spring 38.

As depicted in FIGS. 4A-4D, the detent or latching operation can be effected only if the height of shorter slot 37 is sufficient to permit rocker plate 30 to rock when force isapplied to the downstream one of the treadle plates. Moreover; when force is released from the downstream one of the treadle plates, there is some upward motion of the rocker plate (see arrow C in FIG. 4D) to produce the latched condition; and this upward motion causes the fully opened closure structure to' operation at all, by shortening the height of slot 37 to cannot occur, no latching is effected, i.e., application of forces in sequence to treadle plates 19 and 20 opens the closure structure, and release of force from the downstream one of said plates then causes the structure to automatically reclose. When movable blocking plate 52 is moved upwardly to an extent which permits the aforementioned rocking action, the degree to which the closure structurepartially recloses, to achieve the latched condition when force is removed from the downstream one of the treadle plates 19 and 20, is determined by the height of arcuate portion 52a at the bottom of plate 52. I

It will be appreciated that the structure of FIG. 5 can be modified to incorporate two movable blocking plates of the type shown, mounted side-by-side, to permit the selective blocking or height adjustment of either slot 36 or 37. A structure modified in this fashion, can perform the functions of the detent plate structure previously described in reference to FIG. 3A while simultaneously permitting adjustment of the degree of partial opening maintained in the latched closure conditiOn for either mode of operation.

A further'modification of the structure is shown in FIG. 6. In the arrangements previously described, the treadle plates 19 and 20 bridge the closure structure, i.e., the two treadle plates are disposed on opposite sides of the closure structure respectively. As shown in FIG. 6, however,the two treadle plates 19a and 20a may be disposed completely to one side or theother of the closure element, the location of which'is defined by door frame 12a. This can be effected by the provision of a bracket 12b which extends to one side of the door frame and which supports the treadle plates and associated detent mechanism at the-positions designated 21a, with the actuating cords or cables then being extended over pulleys 60 and 61 and thence upwardly in the configuration already described in reference to FIGS. 1A and 1B.

While we have thus" described preferred embodiments of the present invention, many variations will be suggested to those skilled in the art. For example, the toggle latch mechanism may be modified to include a manually manipulable element for selectively unlatching the detent pin 33 when it is in its latched condition, e.g. to permit the closure structure, when latched into its open position, to be closed without stepping back across the treadle plates. Other variations will be apparent. Inaddition, while two rocker plates and associated detent plates have been described, a single rocker plate and detent plate may suffice, with the opposite side of the treadle assembly being supported for movement in appropriate guides. It must therefore be understood that the foregoing description is intended to be illustrative only and not limitative of our invention, and all such variations and modifications as are in accord with the principles described are meant to fall within the scope of the appended claims.

Having thus described our invention, we claim:

1. A closure structure comprising an elongated support bar, a pair of drapes attached at their upper ends to said support bar and depending therefrom in side-byside relation to one another, a pair of elongated, generally vertical actuating arms mounted for pivotal movement about a common pivot on said support bar, said pivot being located at a position between said pair of drapes, portions of said pair of arms being attached to said pair of drapes respectively at positions vertically below said pivot, a treadle comprising a depressible plate positioned vertically below said support bar, a pair of elongated linkage members extending from said treadle plate to attachment points on said pair of elongated arms respectively, said attachment points being located on portions of said arms disposed on the side of said pivot opposite to the side on which said arm portions are attached to said drapes, spring means coupled to said treadle plate for urging a portion of said treadle plate vertically upward, and means for varying the force exerted by said spring means to control the applied weightwhich will be operative to depress said treadle plate against the force of said spring means to effect pivotal motion of said arms.

The closure'structure of claim 1 including a pair of pulleys affixed to 'said support bar in spaced relation to one another on opposite sides of said pivot, said pair of linkage members comprising elongated cables extending from said treadle plate over said pulleys respectively to said attachment points.

3. The closure structure of claim 1 wherein said treadle comprises a pair of aligned, generally horizontal treadle plates having their adjacent innermost ends respectively mounted below said support bar at positions vertically above their outermost ends, one of said plates extending to one side of said drapes from a position vertically below said support bar and the other of said plates extending to the other side of said drapes from a position vertically below said support bar, and a detent mechanism disposed adjacent the innermost ends of said treadle plates, said detent mechanism including means operative to latch said innermost ends at a depressed position after first actuating forces have been applied to both of said treadle plates, and to release said innermost ends for movement upwardly from said depressed position after second, subsequent actuating forces have been applied to both of said treadle plates.

4. The structure of claim 3 wherein said detent mechanism comprises at least one rocker plate pivotally attached to both of said treadle plates adjacent their innermost ends, a pair of vertically spaced pins extending outwardly from said rocker plate, and a detent plate mounted adjacent said rocker plate, said detent plate 5. The structure of claim 4 wherein said detent plate includes means for adjusting the length of the shorter one of said slots.

6. The structure of claim 4 wherein said detent plate comprises a single longer slot and a pair of shorter slots disposed on opposite sides thereof, and means for blocking at least one of said shorter slots.

7. In combination, a movable closure structure, a treadle assembly for moving said closure structure between first and second positions, said treadle assembly comprising a pair of aligned depressible treadle plates coupled via linkage means to said closure structure, and a detent mechanism coupled to said treadle plates for controlling the treadle-actuated movement of said closure structure, said detent mechanism comprising an angularly movable rocker plate affixed to the innermost ends of said aligned treadle plates, a detent plate disposed adjacent said rocker plate and having a pair of generally vertical slots, of different lengths respectively, disposed in side-by-side communicating relation to one another, means for adjusting the length of at least one of said slots, at least one pin extending outwardly from said rocker plate through said slots for vertical movement in various portions of said slots in dependence upon the angular position of said rocker plate, and resilient means for urging said pin vertically upward relative to said slots, said detent mechanism being operative to latch said treadle plates in a depressed position in response to application of successive actuating forces to said pair of treadle plates se quentially in a first direction and to release said treadle plates for movement away from said depressed position in response to application of successive actuating forces to said pair of treadle plate sequentially in a second direction opposite to said first direction.

8. In combination, a movable closure structure, a treadle assembly for moving said closure structure between first and second positions, said treadle assembly comprising a pair of aligned depressible treadle plates coupled via linkage means to said closure structure, and a detent mechanism coupled to said treadle plates for controlling the treadle-actuated movement of said closure structure, said detent mechanism comprising an angularly movable rocker plate affixed to the innermost ends of said aligned treadle plates, a detent plate disposed adjacent said rocker plate and having a pair of generally vertical slots, of different lengths respectively, disposed in side-by-side communicating relation to one another, said detent plate including means for varying the positions of said pair of slots relative to one another, at least one pin extending outwardly from said having a pair of vertically extending slots of different 7 lengths respectively, said pins extending through said slots for variable movement therein in accordance with the angular position of said rocker plate relative to said treadle plates.

rocker plate through said slots for vertical movement in various portions of said slots in dependence upon the angular position of said rocker plate, and resilient means for urging said pin vertically upward relative to said slots, said detent mechanism being operative to latch said treadle plates in a depressed position in response to application of successive actuating forces'to said pair of treadle plates sequentially in a first direction and to release said treadle plates for movement away from said depressed position in response to application of successive actuating forces to said pair of treadle plates sequentially in a second direction opposite to said first direction. 

1. A closure structure comprising an elongated support bar, a pair of drapes attached at their upper ends to said support bar and depending therefrom in side-by-side relation to one another, a pair of elongated, generally vertical actuating arms mounted for pivotal movement about a common pivot on said support bar, said pivot being located at a position between said pair of drapes, portions of said pair of arms being attached to said pair of drapes respectively at positions vertically below said pivot, a treadle comprising a depressible plate positioned vertically below said support bar, a pair of elongated linkage members extending from said treadle plate to attachment points on said pair of elongated arms respectively, said attachment points being located on portions of said arms disposed on the side of said pivot opposite to the side on which said arm portions are attached to said drapes, spring means coupled to said treadle plate for urging a portion of said treadle plate vertically upward, and means for varying the force exerted by said spring means to control the applied weight which will be operative to depress said treadle plate against the force of said spring means to effect pivotal motion of said arms.
 2. The closure structure of claim 1 including a pair of pulleys affixed to said support bar in spaced relation to one another on opposite sides of said pivot, said pair of linkage members comprising elongated cables extending from said treadle plate over said pulleys respectively to said attachment points.
 3. The closure structure of claim 1 wherein said treadle comprises a pair of aligned, generally horizontal treadle plates having their adjacent innermost ends respectively mounted below said support bar at positions vertically above their outermost ends, one of said plates extending to one side of said drapes from a position vertically below said support bar and the other of said plates extending to the other side of said drapes from a position vertically below said support bar, and a detent mechanism disposed adjacent the innermost ends of said treadle plates, said detent mechanism including means operative to latch said innermost ends at a depressed position after first actuating forces have been applied to both of said treadle plates, and to release said innermost ends for movement upwardly from said depressed position after second, subsequent actuating forces have been applied to both of said treadle plates.
 4. The structure of claim 3 wherein said detent mechanism comprises at least one rocker plate pivotally attached to both of said treadle plates adjacent their innerMost ends, a pair of vertically spaced pins extending outwardly from said rocker plate, and a detent plate mounted adjacent said rocker plate, said detent plate having a pair of vertically extending slots of different lengths respectively, said pins extending through said slots for variable movement therein in accordance with the angular position of said rocker plate relative to said treadle plates.
 5. The structure of claim 4 wherein said detent plate includes means for adjusting the length of the shorter one of said slots.
 6. The structure of claim 4 wherein said detent plate comprises a single longer slot and a pair of shorter slots disposed on opposite sides thereof, and means for blocking at least one of said shorter slots.
 7. In combination, a movable closure structure, a treadle assembly for moving said closure structure between first and second positions, said treadle assembly comprising a pair of aligned depressible treadle plates coupled via linkage means to said closure structure, and a detent mechanism coupled to said treadle plates for controlling the treadle-actuated movement of said closure structure, said detent mechanism comprising an angularly movable rocker plate affixed to the innermost ends of said aligned treadle plates, a detent plate disposed adjacent said rocker plate and having a pair of generally vertical slots, of different lengths respectively, disposed in side-by-side communicating relation to one another, means for adjusting the length of at least one of said slots, at least one pin extending outwardly from said rocker plate through said slots for vertical movement in various portions of said slots in dependence upon the angular position of said rocker plate, and resilient means for urging said pin vertically upward relative to said slots, said detent mechanism being operative to latch said treadle plates in a depressed position in response to application of successive actuating forces to said pair of treadle plates sequentially in a first direction and to release said treadle plates for movement away from said depressed position in response to application of successive actuating forces to said pair of treadle plate sequentially in a second direction opposite to said first direction.
 8. In combination, a movable closure structure, a treadle assembly for moving said closure structure between first and second positions, said treadle assembly comprising a pair of aligned depressible treadle plates coupled via linkage means to said closure structure, and a detent mechanism coupled to said treadle plates for controlling the treadle-actuated movement of said closure structure, said detent mechanism comprising an angularly movable rocker plate affixed to the innermost ends of said aligned treadle plates, a detent plate disposed adjacent said rocker plate and having a pair of generally vertical slots, of different lengths respectively, disposed in side-by-side communicating relation to one another, said detent plate including means for varying the positions of said pair of slots relative to one another, at least one pin extending outwardly from said rocker plate through said slots for vertical movement in various portions of said slots in dependence upon the angular position of said rocker plate, and resilient means for urging said pin vertically upward relative to said slots, said detent mechanism being operative to latch said treadle plates in a depressed position in response to application of successive actuating forces to said pair of treadle plates sequentially in a first direction and to release said treadle plates for movement away from said depressed position in response to application of successive actuating forces to said pair of treadle plates sequentially in a second direction opposite to said first direction. 